This invention relates to improved decorative light tubing of the type disclosed in U.S. Pat. No. 4,271,458, issued June 2, 1981 and to a method of making the improved decorative light tubing.
Decorative light tubing, which is used in hotels, dance facilities, amusement park rides, and along the aisles of movie theatres to provide decorative lighting, consists of hollow, transparent tubing which houses strings of miniature lamps. The lamps are electrically connected via thin wire leads to a pair of supply wires which have a relatively thin insulative coating. The decorative light tubing is formed in a plurality of sections which are interconnectable via an electrical connector at each end of the section. Many such tubing sections can be joined together to form a long length of continuous tubing.
The lamps used in the decorative light tubing are subminiature, low voltage lamps commonly used for aircraft instrument illumination, and have a rated operating life of more than 40,000 hours. When decorative tubing incorporating these lamps is used in calm environments not subject to shock and vibration, the tubing has an operating life of similar magnitude.
When used in environments subject to shock and vibration such as on amusement park rides, the decorative light tubing fails for a number of reasons. The principal cause of failure is fracture of the tungsten lamp filament. This fracture occurs as a result of embrittlement of the filament that occurs during the first thousand hours of energized life. Vibration waves of a frequency and magnitude so minute as to be unmeasurable without extremely sophisticated sensors will, over a period of time, cause the embrittled filaments to break. In addition, the relatively thin welded wire leads and the soldered connections at which they are attached to the supply wires tend to fracture as a result of metal fatigue induced by vibrational bending. The supply wires which interconnect the miniature lamps rub together, eroding their thin insulative coatings and causing subsequent short circuits. With the passage of time, sections of the decorative tubing fail to illuminate as a result of these vibration-induced problems.
One approach to solving these problems has been to substantially fill the interior of the hollow tubing with a substance to damp the vibration of the string of lamps within the tubing as disclosed in U.S. Pat. No. 4,271,458. Specifically, mineral oil or silicone have been used to substantially fill the interior of the tubing. Both the mineral oil and silicone have proven effective in serving as a dampener to protect the electrical lamps and wiring from breakage due to shock and vibration.
While this approach achieves generally good results with respect to solving the problems caused by vibration, it requires substantial labor in manufacture and requires large volumes of damping material which significantly adds to the cost of the tubing. In addition, the damping material contributes to the weight of the finished product which adds to the cost of shipping.